The purpose of the study is to deremine the dosing regimen and safety profile of efavirenz in combination with nelfinavir in children. Recent data indicates that the antiretroviral regimen studied in ACTG 382, efavirenz with nelinavir plus nucleoside reverse transcriptase inhibitors, is well tolerated by a large percentage of HIV-infected children and has a potent antiviral effect, as well as the degree of immune reconstituion, beyond the observation period of 48 weeks specified in the original protocol.